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Near-Far Search: An Evolutionarily Stable Foraging Strategy

Authors:

Uzi Motro & Avi Shmida

Abstract:

This study addresses the momentary rules of foraging behavior on carpet inflorescences. It has long been suggested that patchiness in the distribution of nectar can give an advantage to near-far type of foraging strategies, that is, to foragers which search "near" (in the neighborhood of the last visited flower) as long as the nectar yield is high enough, and go "far" otherwise. Here we show that under certain conditions, such a strategy can be evolutionary stable. Furthermore, prior patchiness in the nectar distribution is not a necessary condition for the evolutionary stability of a near-far search. It turns out that during near-far foraging, some patchiness is created by the foraging process itself, which the near-far forager can exploit later on. To show the evolutionary stability of near-far search, various foraging strategies were compared, according to two, slightly different optimality criteria : the number of flowers emptied during a fixed length bout, and the number of flowers visited until total extraction of the entire inflorescence. We find that long enough bouts (in the case of a single forager) or a substantial probability of revisits to the same inflorescence (in the case of multipleforagers) are necessary for near-far to be an ESS.